This invention relates to a pump drive for an engine and more particularly to an improved arrangement for driving components for the fuel injection system of an engine.
The advantages of fuel injection for application to internal combustion engines are well known. It has been recognized that the performance, particularly of two-cycle engines, can be significantly improved through the use of fuel injection. One form of fuel injection that has been proposed for such applications injects, in addition to fuel, high pressure air into the engine. Although these types of injectors have some advantages, because of the fact that both fuel and air are injected, it is necessary to provide high pressure sources of both fuel and air. This can present some problems, particularly with certain types of application.
Two-cycle engines are widely used for propulsion devices in small vehicles such as motorcycles. However, due to the extremely small space available, it has been difficult to provide a motorcycle engine with the necessary air and fuel compressors for an air/fuel injection system.
It is, therefore, a principal object of this invention to provide an improved and compact pump drive for an engine.
It is a further object of this invention to provide an improved and compact pump and drive arrangement for an engine fuel injection system.
In addition to the normal running conditions of an engine, it is also necessary to supply fuel and air to the engine during starting. Many of the pumps employed with fuel injection systems are driven at a fixed ratio relative to the engine speed so as to generate the appropriate pressure. However, during cranking, the engine speed is quite low and the conventional speed ratio chosen to drive a pump for the fuel injection system may be too slow to insure adequate supply of the fluid being pumped during starting.
It is, therefore, a further object of this invention to provide an improved arrangement for driving a pump from an engine output shaft at a higher speed ratio during starting than during running.
It is a further object of this invention to provide an improved two speed pump arrangement for an injection system of an internal combustion engine.
As is well known, when a fluid is being pumped and compressed, the fluid tends to become heated. This is particularly true when air is being compressed and pumped. The heating of the air can reduce the volumetric efficiency of the pump. Although a variety of cooling arrangements have been employed, these generally rely upon air cooling of the air compressor and do not afford maximum volumetric efficiency.
It is, therefore, a further object of this invention to provide an improved liquid cooling system for the air pump of a fuel air injection system for an engine.
It is a further object of this invention to provide an improved arrangement for cooling the air pump of an injection system of an engine with the liquid cooling system of the engine.